Scientists from the Institute of Agri-Food Research and Technology (IRTA) of Catalonia have analyzed the heat resistance of coronavirus to know the parameters that would have to be considered in a thermal disinfection system that eliminates the pathogen.
The results show that 99.99% of the viral load of SARS-CoV-2 present in closed spaces and surfaces would be inactivated if these are subjected to a temperature of 56? C for 52 minutes or, which would be equivalent, at 65? C for 7.5 minutes.
To carry out the study, the researchers first reviewed the available works on the thermal inactivation of different coronavirus. Then they built a mathematical model with the so-called kinetic parameters of thermal activation, such as the time required to reduce the viral load (DT) and the thermal resistance constant (z) by 90%, which quantifies the sensitivity of the pathogen to the increase in temperature of a treatment.
“Thus we obtained thermal lethality equivalences, i.e. combinations of time and temperature that guarantee a certain level of elimination of the coronavirus, “explains Sara Bover, head of the IRTA Food Safety research program and leader of the study, who clarifies:” This procedure validates a heat treatment against any pathogen, but until now kinetic parameters for coronaviruses had not been described. “
Conditions that affect the viability and survival time of the SARS-CoV-2 virus they don’t know for sure, and the scientific information on its thermal persistence is very scarce. Until now, the temperature that has been taken as a reference to inactivate viruses like this is that of the previous coronavirus, SARS-CoV-1, which is inactivated at a temperature of 56? C for 15 minutes.
“Due to the uncertainty of the available information and the variability between the different coronaviruses, a safer and more conservative estimate of the time required to inactivate the viral load by 99.99% (equivalent to the 4 logarithmic units required of chemical biocides ) would subject infected spaces and surfaces to at least 56? C for 52 minutes, or an equivalent combination, “says Bover.
“If the goal of disinfection out reaching 99.99999% reduction (that is, 7 logarithmic units) of the SARS-CoV-2, for example, in environments with more contamination, such as clinical or hospital, it would be necessary to apply a treatment equivalent to 56? C for 90 minutes, “the scientist points out.
Thermal disinfection vs. chemistry
Research concludes that thermal disinfection can be a good alternative to chemistry in spaces and surfaces with coronavirus because these places remain dry and there is no residue. This heat disinfection could be applied in urban and public environments, specifically, in means of transport such as buses, trains, taxis and ambulances.
In fact, the commission for this study comes from the company Techtrans Systems (OPP group), which had already developed a thermal disinfection system for trucks for the transport of animals, DrySist. With the new data, now what may also adapt in the disinfection of SARS-CoV-2 in public transport vehicles.
The DrySist system was used to disinfect pig transport vehicles against pathogens such as salmonella, Listeria monocytogenes and the virus of porcine reproductive and respiratory syndrome. At the time, IRTA also contributed to the validation of this system developed by one of its researchers, Cristina Castañé, together with OPP group technicians.